Telecommunications networks require a variety of methods to monitor the system performance. One common method of performance monitoring and fault detection of the physical layer of a transmission system is the bit error rate test (BERT). BERT is conducted in the direction of transmission but there are several modes of BERT. In order to sectionalize performance faults, it is useful to verify one-way error rate performance (i.e. from the transmit-end to the receiver-end, called one-way BERT). There is also bidirectional BERT in which one-way BERT is conducted in two opposite directions simultaneously. Another mode is a loopback test (called loopback BERT) in which a looped back performance test is originated from either end of the system with a loopback established at the opposite end of the system.
There are some standard bit error rate test sets available in the art. These commercially available BERT sets contain a generator section and a receiver section. The generator section outputs a serialized data pattern which may be fixed or pseudo-randomized. The receiver section receives a serialized data pattern and verifies it for errors with respect to an expected receive pattern. The generator and receiver sections generally operate independently allowing one-way testing using two BERT sets or looped back testing using a single BERT set. The BERT receiver section also usually contains performance monitoring capabilities by providing error statistics. The BERT set normally provides various interfaces for connection to the generated and received data.
This invention allows the use of a standard bit error rate test set for monitoring the performance of the physical layer of an ATM cell-based transmission system by using a simple 4-signal interface consisting of data to the BERT receiver, data from the BERT generator, and clocks to the generator and the receiver (2 clocks). The invention utilizes the idle cell structure of the physical layer to transport BERT data to conduct a transmission performance test.